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Abstract The objective of this work is to compare mass loss and chemical evolution of the solid phase, versus time, during dynamic torrefaction of different types of biomass. For this purpose, two experiments, ThermoGravimetric Analysis and solid-state 13 C Cross-Polarization/Magic Angle Spinning Nuclear Magnetic Resonance, were run on four representative biomasses. Overall mass loss and chemical evolution of the solid phase were followed, respectively, as a function of temperature and time. Thanks to this coupled information, it was shown that the knowledge of both solid mass loss and chemical evolution is necessary to characterize torrefaction severity. Moreover, biomasses containing higher proportions of xylan lost mass faster than those containing lower proportions. Lignin showed a protecting role towards cellulose, which would lead to a faster degradation of non-woody biomasses in comparison with woody biomasses. Three parameters would have an influence on solid chemical evolution during torrefaction: xylan content in hemicellulose, lignin content in biomass, and cellulose crystallinity.

This paper presents a new methodology that allows to define a 100% renewable smart energy system in a sustainable manner. The authors integrate the EnergyPlan with a mathematical model that analyzes the energy system from an exergetic point of view taking into account the exergy of the whole energy system and its components. Once multiple scenarios are obtained by EnergyPLAN, the exergetic model identifies the scenario characterized by the highest exergetic efficiency and the lowest energy wasting. This approach is a novelty since the "exergetic" optimization criterion coupled with EnergyPLAN software has never been utilized. Since the best energy system could not be economically attractive, this methodology might support Municipalities in setting up focused incentives to make the sustainable solutions the most cost effective too. The authors present a case study by applying the new methodology to the city of Pompeii. The results show that the best solution provides 21.0 MWe capacity of PV plant, integrated to 8.10 MWe of CHP plant. Due to a high value of critical excess electricity production, 10 MWe heat pumps must be installed. Finally, a solar thermal plant is installed. The proposed system could be only realized if new incentives are provided.

Abstract Torrefaction is a thermo-chemical process for upgrading biomass that is usually run at temperatures ranging from 200 to more than 300 °C in an oxygen-free atmosphere and at ambient pressure. It is a useful pre-treatment technology for biomass that significantly alters its physical and chemical composition, making it more efficient in pulverized systems. This paper investigates the grindability of eucalyptus chips torrefied at temperatures ranging from 210 °C to 270 °C for a 15 min residence time, compared to raw material before and after fluidization. The tests were carried out in a cold flow fluidization bed chamber with an internal diameter of 150 mm, with air as the fluidizing medium and a chamber height of up to 750 mm. Biomass grindability was assessed by evaluating the change in particle size distribution. The results showed that the degree of thermal degradation depended on the temperature and was also influenced by particle size. The mean particle size of ground torrefied biomass decreased with an increase in torrefaction temperature. Lastly, for larger particles, it was possible to correlate the size distribution with the severity of the heat treatment by a simple linear equation in our experimental conditions.

A reliable energy supply is fundamental to ensure energy security and support the mitigation of climate change by promoting the use of renewable sources and reducing carbon emissions. Energy system analysis provides a sound methodology to assess energy needs, allowing to investigate the energy system behavior and to individuate the optimal energy-technology configurations for the achievement of strategic energy and environmental policy targets. In this framework, the estimation of future trends of exogenous variables such as energy demand has a fundamental importance to obtain reliable and effective solutions, contributing remarkably to the accuracy of models' input data. This study illustrates an application of regression analysis to predict energy demand trends in end use sectors. The proposed procedure is applied to characterize statistically the relationships between population and gross domestic product (independent variables) and energy demands of Residential, Transport and Commercial in order to determine the energy demand trends over a long-term horizon. The effectiveness of linear and nonlinear regression models for energy demand forecasting has been validated by classical statistical tests. Energy demand projections have been tested as input data of the bottom-up TIMES model in two applications (the TIMES-Basilicata and TIMES-Italy models) confirming the validity of the forecasting approach. (C) 2020 Elsevier Ltd. All rights reserved.

In the present work a novel predictive Wiebe-Based combustion Model (WBM) is proposed for simulation of the combustion process in a normally aspirated 1.6 L spark ignition (SI) engine. Unlike other approaches presented in literature, the novelty consists of: the considered set of Wiebe parameters, that is the angle at 50% of burned fuel, the combustion duration between 10% and 90% of burned fuel, and the form factor m; the nonlinear feature of the used correlations; the set of the involved engine variables, including particularly the laminar burning speed of the air/fuel mixture at combustion start. Based on a wide experimental database a Turbulent entrainment Combustion Model (TCM) is also set up, validated and embedded in a 1D simulation model of the engine. The parameters of the Wiebe function fitting the Mass Burned Fraction (MBF) development are estimated for each engine operating condition and then correlated to main engine variables. To assess to what extent the simpler WBM can be used in place of the TCM, simulations of the validated 1D engine model were carried out with both WBM and TCM and their performances compared in a wide range of engine operating conditions in terms of Brake Mean Effective Pressure (BMEP), Brake Specific Fuel Consumption (BSFC) and Carbon monoxide concentration (CO).

Abstract This paper presents a comparative scaling analysis of two different sized pilot-scale fluidized bed reactors operating with biomass substrates. A multiphase Eulerian-Eulerian 2-D mathematical model was implemented, coupled with in-house user-defined functions (UDF) built to enhance hydrodynamics and heat transfer phenomena. The model validation was attained by comparison to experimental data gathered from both reactors. A grid refinement study was carried out for both geometries to achieve an appropriate computational domain. Hydrodynamics was deeply studied for both reactors concerning the scale-up effect. Mixing and segregation phenomena, solid particle distribution and biomass velocity were matters of great concern. Results showed that UDF implementation successfully minimized deviations and increased the model’s predictability. The largest deviations measured between experimental and numerical results for syngas composition were of about 20%. Solids mixing and segregation was found to be directly affected by the particles size, density, and superficial gas velocity, with the larger reactor revealing improved mixing ability. Improved mixing occurred for smaller particles size ratio (dbiomass = 3 mm), smaller particles density ratio (ρbiomass = 950 kg/m3), and higher dimensionless superficial gas velocities ( U 0 / U m f =3.5). The larger unit showed an increase in near-wall velocity, lateral dispersion, and bubble size. As for the smaller reactor, higher velocities were obtained at the center region due to a more pronounced wall boundary layer. Similarities were found between the two reactors regarding the bubble distribution, dimensionless average bed pressure drop and biomass velocity vector profiles when dimensionless parameters were employed.

Abstract In this paper, a numerical study is conducted in order to investigate the effect of pulsation of air flow at the cathode side of Proton Exchange Membrane (PEM) fuel cell with interdigitated flow field. A two dimensional, isothermal, two-phase, unsteady multi-component transport model is used in order to simulate the transport phenomena. The obtained results are discussed in terms of the influence of flow pulsation on water management and cell performance. The results prove the effectiveness of flow pulsation on improving water removal from cell, enhancing reactants transports to the reaction sites, and increasing the cell performance expressed by increment in the cell limiting current density and maximum output power. The effects of pulsation frequency ( f ), amplitude ( Amp ), and mean inlet pressure ( P in ) on the performance and the output power of the cell, are also investigated. The performance of the cell has no dependency on the frequency range considered in this study. However, as the pulsation amplitude increases the increment in the cell performance is more obvious. Moreover, applying flow pulsation at low flow rates leads to higher efficiency in water removal and performance enhancement.

We study the valuation of preferences for small scale initiatives in renewable electricity generation. We analyse the results of a stated choice experiment among 507 respondents in The Netherlands and provide valuations of characteristics of small scale initiatives. Respondents prefer installing the capacity in small to medium sized groups and their preferred location for the generation capacity is at sea, followed by their own roofs. People that already consume green electricity, as well as those that have indicated to be willing to generate energy locally, are less price sensitive than others. Our results suggest that there is ample scope for expanding the role of micro-generation. © 2014 Elsevier Ltd.